black out of place faces in render
You have some seriously uneven and messed up topology in your mesh, there are vertex overlapping faces, tris mixed with quads and ngons at unexpected places, all that contributes to bad topology and potential artifacts at render time.

Anyway there's an (apparently) useless and undesirable Bevel modifier and the end of your modifier stack causing trouble in the resulting mesh.

It is causing artifacts even in the viewport, and some more in the rendered view. Disabling it seems to mostly fix that problem.

You may want to read up on why quad based topology is important

EDIT

You may also want to remove doubles in your mesh (under edit mode select all and W > Remove Doubles) and recalculate normals (under edit mode select all and Ctrl + N)